Cardiac output during submaximal and maximal work

In the present study oxygen uptake, cardiac output, stroke volume (dye-dilution technique) and oxygen content of arterial blood were determined in 11 women and 12 men, 20–31 years of age, at rest, and when performing submaximal and maximal work. At rest plasma volume (T-1824) and heart volume were determined. Sitting on the bicycle ergometer the stroke volume was 40–90% (mean 63%) of the maximum attained during exercise. Maximal stroke volume was essentially reached at a workload with an oxygen uptake of about 40% of the maximum and a heart rate about 110. No tendency to a decrease in stroke volume was noticed when maximal work was performed. The variation in stroke volume was ±4% during exercise in the range from 40 to 100% of the individual's aerobic work capacity. The maximal cardiac output was 18.5 liters/min for women and 24.1 liters for men. The correlation between heart volume on one side and maximal stroke volume and cardiac output on the other side was high and the expected one from the dimension of the individual. On submaximal as well as maximal exercise the women had a higher cardiac output per liter oxygen uptake than the men, and this can be explained by the lower concentration of hemoglobin in the women's blood. cardiac function during exercise; cardiac output stroke volume; cardiac output and arterial O2 content Submitted on October 3, 1963